1. Field of the Invention
The present invention relates to a TMR magnetic sensor utilizing a tunnel magneto-resistance (TMR) effect, and a method of manufacturing the same.
2. Description of the Related Art
As it is well known that, in a magnetic sensor utilizing the TMR effect (hereinafter referred to as a “TMR magnetic sensor”), when a magnetization direction of a fixed layer and a magnetization direction of a free layer are in parallel with each other, a current flowing through a tunnel oxide film becomes larger, and a resistance value of the magnetic sensor becomes smaller; whereas, when the magnetization direction of the fixed layer and the magnetization direction of the free layer are in antiparallel with each other, the current flowing through the tunnel oxide film becomes smaller, and the resistance value of the magnetic sensor becomes larger. In recent years, active developments have been underway for a rotation angle sensor utilizing such a TMR magnetic sensor. Meanwhile, because the rotation angle sensor is placed adjoining to a rotating member, the sensor is likely to become electrically charged due to static electricity from the outside. In a TMR magnetic sensor using a very thin insulation film of its thickness at several nanometers [nm], the insulation film may be brought to breakdown by an electrical discharge current of the static electricity; for this reason, countermeasures against the static electricity are required from a stage of manufacturing a TMR magnetic sensor element.
As an example in which countermeasure against the static electricity is taken from a stage of manufacturing a magnetic sensor element, for example, according to a conventional technique constituting of a magnetic sensor using a magneto-resistance element (MRE), the technique is disclosed in that, after the magnetic sensor element has been surrounded by a conductive material in a shape of ring, the conductive material is connected to a fixed voltage potential (for example, refer to Japanese Patent No. 5243147).